Electric switch



Jan. 14, 1958 I J. H. FLAT ETA; v '2,820,120'

ELECTRIC SWITCH I Filed Nov. la, 1954 v of? 315' MDM United States Patent() ELECTRIC SWITCH James Howard .Flatt 'and `Harold J. Cromwell, Anderson, Ind., assignors to General Motors lCorporation, Detroit, Mich., a corporationof Delaware Application November 18, 19.514, "Serial No. l469,800

54Claims. (Cl. 200-113) This invention relates to electric switches and is particularly concerned with an improved switch structure that is adapted to alternately make and break an electric circuit.

Switches of the type according to the present invention are frequently used to control lights or other similar devices in electric circuits to cause the lights to operate intermittently. An example of a typical circuit to which the switch isparticularly adapted is a direction signalling system of a vehicle. When the switch is thus used, the signal lights are caused to flash or blink and the warning effect of the sign-al system is considerably increased. Switches to be suitable for use in installations of this type, must be rugged in construction, dependable in operation, economical to manufacture, and have an audible sound during operation.

It is an object therefore of the present invention to provide a switch that is adapted to be used in a signalling circuit of a vehicle; and to .provide the switch with a contact actuating means that comprises a thermoresponsive element or wire and a snap acting contact .actuator. The wire, which is adjusted when cold by an adjustment which is carried by a support, has an end connected with a movable end of a contact actuator so as to place the actuator under .stress when .the wire is cold; which tension is relieved when the wire elongates in response to the heat generated by current passing .therethrough; so that the stress on the actuator is relieved and a mating engagement between a stationary contact and a movable contact carried by the actuator is broken. The contact actuator, formed of a slotted uni-metal part, has a stressed `portion which is formed by lengthening the material of the part disposed between two adjacent slots .and has the movable contact centrally carried on the stressed portion which is moved with a snap action as the stressed portion snaps over center relative to other portions of the metallic part when the distance between the 4free end ancl ixed end of the actuator is varied in response to the variations in tension as applied by the `w1re. f

To further carry out the above objects, it is another .object of the present invention to provide a means in kthe switch for transmitting the sound of the snap acting contact actuator to a case for the switch to increase the audibility of said sound.

In carrying out the above object, it is another object of vthe present invention to provide the tensioned wire with a-capstan screw adjustment for varying the tension on said Contact actuator.

A further object of the present invention is to provide -an electric switch with a snap acting contact actuator which is formed of a single piece of metal that has one .end-lixed toa support and has the other end freely movable', the actuator when formed is provided with longi- `which stressed portionrnoves a contact carried centrally 2,820,120 Patented Jan. 14, 1958 2 thereon Jwith a snap action in accordance with variations in tension which is applied to the free end of said actuator by a `thermoresponsive element.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure l is a view, partly in section, of a switch according lto the present invention.

Figure 2 is a view in the direction of the arrows 2-#2 `along-the line 2--2 in Figure l.

Figure 3 is a view, partly in section, along vthe line 3-3 in Figure l.

Figure 4 is a view, partly in section, along line vin Figure 3.

Figure 5 is a perspective view of a snap acting 'contact actuator as utilized in the switch according to the present invention.

In the drawings the numeral 20 is used to designate ka switch which is provided with an insulated base/22 whereon an insulated support 24 is suitably secured. The support 24 is provided with a base portion 26 and an Vend portion`28 which defines a rpair of arms 30 and 32. The base portion 26 supports a pair of terminals 34 and 36 in spaced relation. The terminals 34 and 36, extending through suitably located apertures in base 22, are maintained in position on the base portion 26 by a rivet 38 which has an upset portion 40 insulated from terminal 34 by a grommet 42. The end -37 of rivet 38, which vis in contact with terminal 36, is maintained in position'by the head 44 of rivet 38, which is tightened when the upset portion 40 is formed and maintains the terminals 34 and 36 in position on support 26. The end 37 of rivet '38 also has a slot 35 therein so that the rivet -will act as a capstan, the purpose which will be hereinafter apparent.

The terminal 34 also has an extending end portion 46 which has a threaded aperture 48. The aperture 48 is adapted to adjustably receive a stationary contact element 49 which has threads thereon so the contact 49 may be adjustably moved relative to base portion 26 when the threaded portion of elementV 49 is turned in aperture 48.

A contact actuator 50, most clearly seen -in yFigure 5, has a fixed end 52 secured in support 26 and a freely movable end 54 disposed to ride upon the arms 30 and 32 of the arms of end 23 of support 24. The contact actuator 50, formed of a single unitary metallic part, has two longitudinally extending slots 56 and 58 which define a center portion 69 which is placed understress relative to the other portions of the actuator 50 when the material forming this center portion is lengthened. .The free, end portion 54 is provided with a V-shaped portion 62 which is adaptable to ride upon the arms 30 and 32 and be moved relative thereto in response to variations in the tension of a thermoresponsive wire 64. This wire .64 has one end passing through an aperture 65 and suitably secured as by soldering in the apex of the V-shaped bent portion 62. The other end 63 of the wire ,64 is secured in the slot 35 of the adjustment rivet 38.

A movable contact 68, preferably centrally secured to the .stressed portion 60 of the contact actuator, Ais normally maintained in mating engagement with contact element 49 when sufficient tension is lapplied to the cold thermoresponsive wire 64 to cause the free end 64 to b e moved toward the support 26. When the parts of the switch are in this position, a current may be conducted from .terminal 34 through contact element 49, Contact clement 68, contact actuator 50, .thermoresponsive wire 64, adjustment screw 38 to'terminal 36. This current through wire 64 will cause the sameto become 'heated and elongate. The elongation of the wire 64 reduces the tension applied thereby on the free end 54 of the contact actuator 50. This relief of tension will permit the ,end 54 of actuatorSG to move away from the xed end 52. The movement of end 54 in this fashion will cause the curve of the stressed portion 60 to tend to be inverted and to move with a snap action through a plane defined 4by the outer portions of actuator 50, so that the curve of the stressed portion 60 is reversed and the mating engagement `between contacts 49 and 68 is broken. The breaking of the engagement between the contacts 49 and 63 will cause a flow of current through wire 64 to cease and permit the wire tocool and contract and reapply a tension A portion adjacent the end 63 of wire 64 is wrapped s about screw 38.` This arrangement will provide a capstan whereby the tension on wire 64 may be varied so that the tension on the contact actuator may be varied. This variation of tension will provide an adjustment for the time cycle of operation of the switch. It is apparent that van adjustment of the tension of wire 64 will affect not only .the cycling time but the range of movement of the contact 68. This movement of the contact may result in an improper engagement between contacts 49 and 68. The proper adjustment of the stationary contact 49 will compensate for this change in movement. This adjustment may be accomplished by threading the adjustment station- ,ary contact 49 within the threaded aperture 48.

A cover 72 is also provided for the switch 20 to enclose and protect the various parts of the switch against damage,

etc. One of the advantages of the present invention is that the snap action movement of contact actuator is accompanied by a clicking sound. The effect of this clicking sound is audibly increased by a sound conducting element 74 which has one end secured to the stationary contact carrying portion of terminal 34 and the other end in engagement with the cover 72 so that the cover acts as a sounding board and audibly increases the clicking `sound of Contact 5i). This increase in audibility of sound is very important when the switches of the type shown are installed in a vehicle turn signal system as many states have laws requiring an audible sound to indicate .that the turn signal system is propery operating.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An electric switch, comprising; -a support, a pair of spaced arms extending from said support, a stationary contact carried by said support and spaced from said arms, a movable contact adapted to mate with said stationary contact and means for reciprocatively moving said movable contact relative to said stationary contact for alternately making and breaking the mating engagement therebetween, said means comprising; a contact actuator having one end fixed to said support and the other end freely movable with a slidable engagement with said arms, said actuator being formed of a single piece of metal having at least one slot therein so as to divide the piece into portions, one of which is stressed so that the member will impart a snap action movement to the movable contact which is centrally secured to one of said portions, and a current conducting tensioned thermoresponsive means adapted to elongate and contract in rcsponse to a iiow ot current therethrough having one end secured to the free end of said actuator for controlling the sliding movement of said free end on said arms and a 4means carried by said support and connected to the "other end of said thermoresponsive means for adjusting of spaced arms extending from said support, a pair of terminals carried by said support, a stationary contact electrically connected with one of said terminals and adjustably carried by said support in spaced relation to said arms, a movable contact adapted to mate with said stationary contact, and a means electrically connected with said other terminal and adapted to reciprocally move said movable contact relative to said stationary contact for alternately making and breaking said mating engagement, said means comprising; a contact actuator having one end lixed to said'support and the other end movable with a sliding movement on said arms, said actuator being formed of a single piece of metal having at least one slot therein dividing the piece into at least two interconnected portions, one of which is stressed so that the member will embody a snap action in response to the sliding movement of said movable end, said movable contact being centrally carried by said stressed portion and moved thereby into and from said mating engagement, and a current conducting thermoresponsive means adapted to be heated and elongate and contract in response to the lilow of current therethrough, said thermoresponsive element having one end electrically connected to the freely movable end of said actuator and tensioned when cool to move said free end for causing the mating of said contacts, said element having the other end adjustably carried by said support and electrically connected with said other terminal whereby the ow of current through said thermoresponsive means when said contacts mate causes the thermoresponsive means to heat and elongate whereby the tension on the free end of said actuator is relieved and the portion of said actuator carrying said movable contact is caused to move with a snap action for breaking the mating engagement with said stationary contact.

3. In an electric switch, the combination comprising; a support, a contact actuator having one end fixed to the support and the other end freely movable, said contact actuator being formed of a slotted single piece of conducting material an-d having an integral center portion formed between slots in said material and having said central portion lengthened suiciently to place said portion under stress to cause said actuator to embody a snap action, a movable contact electrically secured to said center portion, a current conducting thermoresponsive wire having one end connected with said support and the other end connected under tension with the free end of said actuator when said wire is cool so that the movable contact is in mating engagement with a stationary contact carried by said support, said wire being adapted, when heated in response to current owing through said mating contacts, to elongate and relieve the tension applied to the free end of said actuator for causing the central portion thereof to move with a snap action for breaking the engagement between said contacts, a cover for said switch and a sound conducting means secured to said stationary contact and in contacting engagement with the cover whereby sounds which accompany the snap action lengagement of said contacts is transmitted to said cover.

4. In an electric switch, the combination comprising; a support, a stationary contact carried by said support, a support for the stationary contact, a snap acting contact actuator carried by said support, a second contact movable by said actuator with a snap action into and from a mating engagement with said stationary contact, a cover for said switch and means including a member secured to the support for the stationary contact and in contacting engagement with the cover for said switch for transmitting sounds which accompany the snap action engagement of said contacts to said cover.

5. In an electric switch, the combination comprising; a support, a pair of contacts, a means for moving one of said contacts with a snap action relative to the other contact, a cover for said switch and a sound conducting means includ-ing a member secured to a support for one of said contacts and in contacting engagement withfthe cover whereby sounds which accompany the snap acting engagement of said contacts lare transmitted t0 said cover.

References Cited in the le of this patent UNITED STATES PATENTS 6 Schmidinger Oct. 27, 1942 Barton June 17, 1952 Boddy Mar. 16, 1954 Midgley Aug. 24, 1954 Harmon Jan. 18, 1955 FOREIGN PATENTS Sweden Sept. 10, 1946 Great Britain June 30, 1954 

